Recent advances in immunologic techniques permit the cloning and maintenance of human T-cells that are then available for detailed scientific study. In addition, monoclonal antibodies have been developed that recognize human T-lymphocytes at various stages of differentiation and identify different functional categories of T-cells. Anti-Ta1 is one such monoclonal antibody that reacts with activated T-cells that are more prevalent in the blood of multiple sclerosis patients compared to controls. These approaches will be used for a series of detailed investigations of cellular immunologic studies of central nervous system inflammatory disease, with particular emphasis on multiple sclerosis, a presumed autoimmune disease of the central nervous system associated with abnormalities of cellular immunity. The specific areas of investigation and questions to be asked are as follows: 1. What are the phenotypes and functional characteristics of activation antigen positive cells in the blood and spinal fluid of MS patients and patients with other inflammatory CNS diseases? 2. Using direct single cell clonal analysis of blood and cerebrospinal fluid T-lymphocytes, what is the frequency of different T-cell subpopulations using functional and phenotypic analysis? 3. Are there deficiencies in white matter antigen specific T8 suppressor cells which are induced by T4 suppressor/inducer cells in patients with multiple sclerosis? 4. What are the effects of virus on in vitro immune function and, in particular, the interaction of reovirus type 3 with specific T-cell subpopulations that have a receptor for the viral hemagglutinin?